Replace leaking wing tank. Adding tank to wing with no tank. Need help.

34 posts in this topic

Posted (edited)

I have a KF 4 with a 13 gal fiberglass tank in the right wing and in the left wing is a locker and no tank.

Question is, My left wing with just the wing locker. Can the internal wing structure be changed to accommodate a 6 or 13 gallon tank? The  cross braces are different for each configuration but once the brackets are riveted in place, that's it, they can't be changed. Is that right or not?

My fiberglass tank, right wing,  has been sloshed and held for a year but it's coming apart again and it's time to retire it. So it's getting replaced for sure.  It's the older fiberglass and the previous owner let her sit for months with ethanol fuel. 

Or better yet, does anyone have a set of KF4 speedster wings with 13 gallon tanks? 

 

IMG_20150731_101221.jpg

Edited by rdooley79
Better title for topic

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Posted (edited)

If you cant leave a bracket in place and add another to change the configuration of the drag braces, then after removing a bracket you can put blind rivets back into the original spar holes and it should be OK.  Sounds like a re-cover job for both wings anyway.  If you don't have the newer type brackets, the same goes for the end of the drag brace removed.

EDMO

Edited by EDMO

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Posted (edited)

There was a discussion about replacing a wing tank but making the top wing covering out of thin aluminum rather than wood/fabric and using a piano hinge with 1/4 turn flush fasteners to hold it shut, just like the storage locker. 

Seems like a good way to go. Allows easy access/inspection and replacement of the tank later on but will there be any structural degradation that way?

 

She's flying great and most of the time the single 13g tank is more than enough. I've also got two 1.9g header tanks in parallel behind the seats as a reserve. That will get me 45 minutes of flight time at a normal burn rate. So really it's a true 13 gallon usable. Not bad. 

 

Thoughts guys/ suggestions?

 

 

Edited by rdooley79

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Posted (edited)

For the locker just leave be and add a bladder tank,I have recently purchased a 15 litre (6gal?)tank that is a perfect fit,the intention was to tee into one of the tank lines and let gravity do the rest(no venting issues) unfortunetly i wont get a chance to try it as KNZ is currently for sale as i am refurbishing another fox,I will try and get to the hanger today and get some photos of the tank and fit

perhaps a large custom  made bladder could be installed  in the main tank,fuel level checking would be the only drawback.   No more leaks to worry about!

Just a thought ,cut the top out of the glass tank to get access,glass and then add a devider to that tank ,making it a 6gal then plumb in a 6 gal bladder in the remaining half?

Edited by Dusty

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Posted (edited)

Has anyone used thin aluminum as a skin over the wing fuel tank? 

Is there any reason that I couldn't use a thin aluminum skin with a piano hinge and six 1/4 turn fasteners, just like the cargo locker, just bigger. 

Would it loose any strength?

That would allow me to open it up and inspect,run wires, or remove the tank without having to paint/cover. 

 

Haven't run across anyone else with an access panel for their wing tank, seems like a good option.   

I haven't worked with fabric before but do have the Stits book to reference but am freaked out by cutting in to the wing and especially painting and finishing it nicely as well. That's why I wonder about using aluminum for the skin over the tank, so I don't have to work with the fabric much. Fabric freaks me out, the repair finish is not as good as the original finish and I just hate making another blemish. Thin aluminum shouldn't be much difference in weight than the wood/dope/fabric/paint. Plus it's just the metal painted to match the plane and that I am more comfortable with doing that, seems more straight forward.

Is the aluminum skin idea just dumb? Should just got with fabric or what do you guys think?

 

Kitfox is closed until next Monday the 4th, so I want to get all my other supplies lined up in the mean time. 

Should I order anything else from KF other than the replacement tank?

 

 

Thanks Guys. I need some guidance here. This is the last thing I wanted to do to the plane.

 

 

Edited by rdooley79

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Posted (edited)

I don't know if this will work for you, but Avid put a fiberglass cover over the wing tanks  (I only have the manual for the Magnum) - If you could get them from the supplier we have on here, they should match the wing profile, and maybe you could hinge them and add the fasteners.  I think this might be better than aluminum.

One other thing - the fabric is pulling on the root rib - If you wrap around and end the fabric at the rib outboard of the tank, you may need to brace that rib.

Now, if someone can help me out here, and list the guy who makes the fiberglass for Avids....I forgot to take my memory pills today!

EDMO

Edited by EDMO

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Posted

I don't know if this will work for you, but Avid put a fiberglass cover over the wing tanks  (I only have the manual for the Magnum) - If you could get them from the supplier we have on here, they should match the wing profile, and maybe you could hinge them and add the fasteners.  I think this might be better than aluminum.

One other thing - the fabric is pulling on the root rib - If you wrap around and end the fabric at the rib outboard of the tank, you may need to brace that rib.

Now, if someone can help me out here, and list the guy who makes the fiberglass for Avids....I forgot to take my memory pills today!

EDMO

Added:  If you could get this fiberglass skin WITHOUT the hole for the gas filler tube, then you could put your own hole in it to match the Kitfox tanks.  EDMO

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Posted

Don't let the thought of doing fabric freak you out.  It is really easy to do and the painting is a snap with PolyFiber products, well Polytone for sure.  Get the PolyFiber manual and have some fun.

 

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Posted

+1 to Paul's comment. 

Fabric work is not difficult and painting poly fiber products is a cake walk.  You would be making things a million times harder with some type of cobbled aluminum or fiberglass cover.

Cut the fabric. 

Replace the tank with a new alcohol resistant one. 

Repair and repaint the fabric.

Go flying.  

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Posted

I installed the plastic wing tanks inside my crap fiberglass tanks. Instead of covering it with fabric again I covered it with aluminium. At the leading edge I just used fabric for the hinge then screwed the rest to the ribs. Now I can access the tanks with no trouble. As a matter of fact tomorrow I have to open it up and replace the fuel line. I would never cover it with fabric again. I will take pictures tomorrow if I make it over there.

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Posted

I don't know if this will work for you, but Avid put a fiberglass cover over the wing tanks  (I only have the manual for the Magnum) - If you could get them from the supplier we have on here, they should match the wing profile, and maybe you could hinge them and add the fasteners.  I think this might be better than aluminum.

One other thing - the fabric is pulling on the root rib - If you wrap around and end the fabric at the rib outboard of the tank, you may need to brace that rib.

Now, if someone can help me out here, and list the guy who makes the fiberglass for Avids....I forgot to take my memory pills today!

EDMO

Ed I never braced my rib. No problems so far.

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Posted

I don't know if this will work for you, but Avid put a fiberglass cover over the wing tanks  (I only have the manual for the Magnum) - If you could get them from the supplier we have on here, they should match the wing profile, and maybe you could hinge them and add the fasteners.  I think this might be better than aluminum.

One other thing - the fabric is pulling on the root rib - If you wrap around and end the fabric at the rib outboard of the tank, you may need to brace that rib.

Now, if someone can help me out here, and list the guy who makes the fiberglass for Avids....I forgot to take my memory pills today!

EDMO

Ed I never braced my rib. No problems so far.

Probably since the fabric has already been shrinked, he will be OK.  I would brace it the same as the root rib is braced if a re-cover.

EDMO

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Posted

I'm very happy to see this thread take form.  I too have a slowly disolving wing tank; mine in an avid.  I had the lucky fortune of making contact with a gentleman in AR who had 2 flat bottom wing tanks that I think will fit my bird.  I'll start taking picture and measurements and report findings here.

One interesting note: I drained my tank a couple of weeks ago to replace fuel lines.  Upon refilling it I discovered that it holds 15 gallons, not the "advertised" 13.  Draining took place through the fitting that feeds the header tank.  I left the fuel flow meter set up for 13 gal at full, It's just nice to know a couple extra gallons are in there.  Perhaps the extra volume is gained by not having the undercamber shape?

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Posted

 

Now, if someone can help me out here, and list the guy who makes the fiberglass for Avids....I forgot to take my memory pills today!

EDMO

Call Rod at Performance Products LLC  (208) 761-8244 

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Posted

This is how I did my tank insert access. Not pretty but very practical. I would rather have practical than pretty.

IMAG0739.jpg

IMAG0740.jpg

IMAG0741.jpg

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Posted

Just for argument's sake, I believe the fabric does not contribute to the structural strength of the aircraft, at least from an analytical point of view. The practical point is that stretched fabric has some shear strength, but I bet the structure meets all criterion with just the spars and ribs, and it uses the fabric as the way to assure good air passage for aerodynamic effect.

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Posted

Just for argument's sake, I believe the fabric does not contribute to the structural strength of the aircraft, at least from an analytical point of view. The practical point is that stretched fabric has some shear strength, but I bet the structure meets all criterion with just the spars and ribs, and it uses the fabric as the way to assure good air passage for aerodynamic effect.

Very true - but it sure makes the takeoff a lot shorter if you have a cover on the ribs and spars!

EDMO

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Posted

Just for argument's sake, I believe the fabric does not contribute to the structural strength of the aircraft, at least from an analytical point of view. The practical point is that stretched fabric has some shear strength, but I bet the structure meets all criterion with just the spars and ribs, and it uses the fabric as the way to assure good air passage for aerodynamic effect.

Very true - but it sure makes the takeoff a lot shorter if you have a cover on the ribs and spars!

EDMO

Ed, I believe this is addressed by the phrase, "and it uses the fabric as the way to assure good air passage for aerodynamic effect".  Nonetheless, your comment gave me a hearty chuckle!:BC:

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Posted (edited)

Bandit,  what thickness alu did you use? How did you bend it to match the shape of the wing, or is it thin enough that just fastening it will shape it?  What fasteners are you using?

Edited by Knuckledragger

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Posted

Bandit,  what thickness alu did you use? How did you bend it to match the shape of the wing, or is it thin enough that just fastening it will shape it?  What fasteners are you using?

I was also wondering how you attached it at the front.

EDMO

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Posted

In his first message on this topic, Bandit said that he used the fabric as the hinge for the front of the aluminum.  Jim Chuk

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Posted

Bandit,  what thickness alu did you use? How did you bend it to match the shape of the wing, or is it thin enough that just fastening it will shape it?  What fasteners are you using?

I don' t remember what thickness the alu was. It is light enough to follow the curve of the wing. The fasteners I used pressed into a hole I drilled into the ribs, then drilled the alu and screwed it down. I think the screws are 10/32. I also ran a row parallel to the front spar. For the hinge I just used fabric glued to the front spar.

 

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Posted

Bandit,

I don't understand what you mean by "The fasteners I used pressed into a hole I drilled into the ribs"  Maybe a couple of pics would help?  Since you used 10/32 machine screw fasteners around the outside edge, I guess you installed nuts somewhere as well?

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Posted

Bandit,

I don't understand what you mean by "The fasteners I used pressed into a hole I drilled into the ribs"  Maybe a couple of pics would help?  Since you used 10/32 machine screw fasteners around the outside edge, I guess you installed nuts somewhere as well?

I think they are called blind nuts or rivnuts. Drill the hole and press them in. They are threaded on the inside. If I did it again I would put a little epoxy on them before I pressed them in.

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Posted (edited)

Got it!  It all makes sense now, I think. :)

http://amzn.to/1YR7sOO

41FMvjt8i9L.jpg

Edited by Knuckledragger

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